Diamond drill bit



April 1967 A. B. HILDEBRANDT v 3,314,490

DIAMOND DRILL BIT F iled March 31, 1965 FIG. 2

BYW E. L

ATTORNEY United States Patent 3,314,490 DIAMQND DRILL BIT Alexander B.Hiidehrandt, Tulsa, Okla, assignor to Esso Production Research Company,a corporation of Delaware Filed Mar. 31, 1965, Ser. No. 444,272 4(Ilairns. (Cl. 175-329) The present invention relates to rotary bits fordrilling boreholes in the earth and is particularly concerned withdiamond bits for drilling oil wells, gas Wells and similar boreholes.

The typical diamond bit employed in the petroleum industry includes abody provided with a steel shank and a crown composed at least in partof a metallic matrix in which the diamond cutting elements are embedded.The matrix is generally formed by the liquid phase sintering of tungstencarbide or a similar refractory hardmetal powder in the presence of asofter binder metal. Experience has shown that erosion of the matrix bythe fluid used to remove cuttings from the borehole is a seriousproblem. Efforts to avoid this problem through the use of improvedtungsten carbide compositions, more erosionresistant binder metals,higher tungsten carbide-to binder metal ratios, and other changes in thecrown metallurgy have been only partially successful. Furtherimprovements which will facilitate the use of high circulation rates tosecure adequate cleaning of the diamonds and will permit high drillingrates without severe erosion and premature loss of the diamonds areneeded.

It is therefore an object of the present invention to provide improveddiamond bits for drilling oil wells, gas wells and similar boreholes inthe earth. Another object is to provide diamond bits which willfacilitate the use of high fluid circulation rates to secure better bitperformance during rotary drilling operations carried out in thepetroleum and mining industries. A further object is to provide bitswhich are less susceptible to matrix erosion and loss of the diamondsthan diamond drilling bits available in the past. Still other objectswill become apparent as the invention is described in greater detailhereafter.

In accordance with the invention, it has now been found that theperformance of a diamond drill bit can be improved by providing anelongated throat opening which extends across the lower surface of thetool and feeds the discharged drilling fluid into substantially parallelwaterways extending outwardly from the throat opening to the gagesurfaces. This arrangement of the throat opening and waterways reduceserosion of the matrix in the critical area of the throat where severeerosion normally takes place and promotes more effective distribution ofthe fluid to the diamond-bearing surfaces between the waterways than cangenerally be obtained with bits having radial or spiral waterways ofconventional design. This in turn facilitates the use of higher fluidcirculation rates to promote better bit performance.

The nature and objects of the invention can best be understood byreferring to the fol-lowing detailed description of one embodiment ofthe improved bit and to the accompanying drawing in which:

FIGURE 1 is a vertical elevation, partially in section, of a diamonddrill bit constructed in accordance with the invention; and,

FIGURE 2 is a bottom view of the bit shown in FIG- URE 1.

The diamond bit depicted in the drawing includes a cylindrical body 11having an upper shank 12 on which external threads 13 have been cut topermit attachment of tool to the lower end of a rotary drill string orthe outer rod of a mining drill. The body will normally be cast ormachined from steel or a similar tough, shock from about 50 to about ofthe crown diameter.

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resistant metal. If the tool is intended for use in the petroleumindustry, the shank dimensions and threads will generally be selected toprovide a standard API tool joint pin. Standards are similarly availablefor tools to be employed in the mining industry. In lieu of a shankhaving external threads as shown, a tool joint box containing internalthreads may be provided. The body includes an axial passageway 14 whichextends through the body from an opening in the upper shank and permitsthe circulation of drilling fluid to the tool. The body is provided withexternal threads 15 at its lower end to facilitate attachment of thecrown before it is Welded in place at the lower end of the body. Thewelded joint is designated by reference numeral 16 in FIGURE 1.

The crown of the bit depicted in the drawing extends outwardly beyondthe upper part of the body to provide gage surfaces 17 which contact theborehole wall and assist in maintaining the desired borehole diameter.The crown includes a generally tubular crown blank 18 of steel orsimilar metal to which the body is attached, a matrix 19, and diamondcutting elements 20. The matrix is bonded to both the inner and outersurfaces of the crown blank. These surfaces may be roughened or indentedto promote better bonding. The crown is normally formed by placing thediamonds in shallow depressions in the wall of a refractory mold of thedesired shape, positioning the crown blank in the mold, surrounding theblank with finely ground tungsten carbide powder or a similar hardmetal,and then infiltrating a molten copper-nickel alloy or equivalent bindermetal into the interstices between the powder granules. The binderemployed will generally have a melting point between about 1550 F. andabout 2450 F. and in the molten state should have the ability to wet thehardmetal granules. As the binder metal cools following the infiltrationstep, a metallurgical bond between the steel surfaces and the carbidegranules is formed. The diamonds are held in place by the surroundingmatrix. The crown may then be removed from the mold, sand blasted toremove surface irregularities, and thereafter attached to the body. Analternate procedure which may 'be utilized in lieu of that describedinvolves the liquid phase sintering of an intimate mixture of carbidepowder and bonding metal at high pressure and elevated temperature.These and other fabrication methods and matrix compositions which may beemployed are described in greater detail in the Diamond Drill Handbookby I. D. Cumming, 1956 edition, published by J. K. Smit & Sons ofCanada, Ltd, Toronto.

Below the gage surfaces, the lower part of the crown shown is rounded togive a generally concave lower surface or drilling face 21. As can beseen more clearly from FIGURE 2 of the drawing, this surface includes anelongated slot-like throat opening 22 which communicates with passageway14 in the body and upper part of the crown. The opening extends asubstantial distance across the crown, preferably through a distanceequivalent to It decreases in depth toward its outer ends and isgenerally of substantially uniform width. Alternatively, the depth maybe substantially uniform and the width may decrease toward the bitperiphery. The diamonds 20 which serve as cutting elements are embeddedin lands 23 which extend at substantially right angles to thelongitudinal axis of the throat opening. Each land contains one or morerows of diamonds. At the center of the bit, the lands extend inwardlybeneath the bit axis to permit drilling out of the formation at thecenter of rotation and thus avoid the formation of a core. The diamondconcentration at this point will generally be somewhat greater than atother points on the tool because relatively little motion takes placebetween the diamonds and underlying formation. The two outermost lands24 at the ends of the throat opening on the bit shown contain nodiamonds and extend a short distance below the other lands to divert theflow of drilling fluid. In lieu of these diversion lands, lands similarto those elsewhere on the bit may be utilized. Waterways 25 extendingoutwardly from the throat opening at substantially right angles to thelongitudinal axis of the opening separate the adjacent lands. Thewaterways and intervening lands extend upwardly on the gage surfaces toprovide lateral stability and permit the escape of drilling fluid intothe annular space surrounding the body of the bit. The cross-sectionalareas of the waterways may decrease toward the outer ends of the throatopening to secure more uniform fluid distribution. Each waterway mayalso be tapered to control the pressure drop along its length ifdesired. Junk slots 26 are provided in the gage surface adjacent thediversion lands 24' to serve as passageways through which particlesproduced by the diamonds may escape without being reground between thegage surfaces of the tool and the surrounding borehole wall. The bitshown includes two diametrically opposed junk slots but a single slot ormore than two may be provided if desired.

As can be seen from the cross-sectional view in FIG- URE 1, the bitdepicted is provided with a concave lower surf-ace having a radius ofcurvature substantially equivalent to the radius of the borehole. Therim surrounding the concave spherical surface is rounded to avoidexcessive forces on the diamonds near the bit periphery. This type ofconfiguration reduces the tendency of the bit to walk" or tilt inresponse to wob-bling of the drill collars above it and minimizesvariations in the forces acting on the diamonds. This reduces diamondlosses and promotes longer bit life. p

- In drilling with the tool of the invention, drilling fluid iscirculated downwardly through the drill string to which the bit isconnected. The fluid passes through passageway 14 in the body and upperpart of the crown and emerges into throat opening 22 in the lower partof the 'tool. Because of the relatively large cross-sectional area ofthis opening, there is littletendency for the emerging fluid to erodeaway the matrix. In conventional diamond bits, on the otherhand, erosionis normally severe at points around the throat where the fluid firstflows between the matrix surface and the underlying formation. The fluidthus supplied to the throat opening flows outwardly through waterways 25into the annulus above the crown, carrying with it cuttings produced bythe diamonds. Because the fluid is fed from the enlarged throat openinginto a series of parallel waterways across which the pressure drop doesnot. vary widely, fluid welocities beneath the cutting surfaces aresubstantially uniform. Better fluid distribution is obtained than can besecured with a tool having radial or spiral waterways extendingoutwardly from a relatively small throat opening. The use of junk slotsfacilitates the removal of solids beneath the bit without repeatedregrinding and also simplifies tripping of the bit into and out of theborehole.

It will be understood that the invention disclosed herein is not limitedto the specific tool shown in the drawing. The junk slot configurations,the number and size of the waterways, the fluid diversion lands andother features may be modified without departing from the invention.Cutting elements other than diamonds, regular or irregular shapedparticles of tungsten carbide, a multiple carbide or similar hardmetalfor example, may be employed if desired. These and other modificationsof similar nature will readily suggest themselves to those skilled inthe art.

What is claimed is: a

1. A rotary drill bit comprising:

(a) a body member containing an axial passageway for the transmission ofdrilling fluid, said member including means for connecting said bit tothe lower end of a drill string;

(b) a crown connected to the lower end of said body member and extendinglaterally beyond said memher, said crown including (i) a lower face forcontasting the formation at the bottom of a borehole, (ii) an elongatedslot-like throat opening in said lower face, said throat openingcommunicating with said passageway in said body member near thelongitudinal axis of said bit, (iii) a plurality of waterways in saidlower face extending from said throat opening to the crown periphery atsubstantially right angles to the longitudinal axis of said opening, and(iv) diversion lands extending at substantial right angles to thelongitudinal axis of said throat opening at the ends thereof; and,

(c) a plurality of diamonds embedded in lands on said lower face betweensaid watercourses.

.2. A bit as defined by claim 1 wherein said throat opening is ofsubstantially uniform Width and decreases in depth toward each endthereof.

3. A bit as defined by claim 1 wherein said throat opening is ofsubstantially uniform depth and decreases in width toward each endthereof.

4. A bit as defined by claim 1 wherein said throat opening extends atleast halfway across said crown.

References Cited by the Examiner UNITED STATES PATENTS 791,264 5/ 190 5Hardsocg 4l7 X 2,264,440 12/1941 H-avlick 175329 2,545,195 3/1951 Crake175-330 2,998,088 8/ 1961' Pennington 175-329 3,153,458 10/1964 Short175-329 CHARLES E. OCON'NELL, Primary Examiner.

R. E. FAVREAU, Assistant Examiner.

1. ROTARY DRILL BIT COMPRISING: (A) A BODY MEMBER CONTAINING AN AXIALPASSAGEWAY FOR THE TRANSMISSION OF DRILLING FLUID, SAID MEMBER INCLUDINGMEANS FOR CONNECTING SAID BIT TO THE LOWER END OF A DRILL STRING; (B) ACROWN CONNECTED TO THE LOWER END OF SAID BODY MEMBER AND EXTENDINGLATERALLY BEYOND SAID MEMBER, SAID CROWN INCLUDING (I) A LOWER FACE FORCONTACTING THE FORMATION AT THE BOTTOM OF A BOREHOLE, (II) AN ELONGATEDSLOT-LIKE THROAT OPENING IN SAID LOWER FACE, SAID THROAT OPENINGCOMMUNICATING WITH SAID PASSAGEWAY IN SAID BODY MEMBER NEAR THELONGITUDINAL AXIS OF SAID BIT, (III) A PLURALITY OF WATERWAYS IN SAIDLOWER FACE EXTENDING FROM SAID THROAT OPENING TO THE CROWN PERIPHERY ATSUBSTANTIALLY RIGHT ANGLES TO THE LONGITUDINAL AXIS OF SAID OPENING, AND(IV) DIVERSION LANDS EXTENDING AT SUBSTANTIAL RIGHT ANGLES TO THELONGITUDINAL AXIS OF SAID THROAT OPENING AT THE ENDS THEREOF; AND, (C) APLURALITY OF DIAMONDS EMBEDDED IN LANDS ON SAID LOWER FACE BETWEEN SAIDWATERCOURSES.